Synchronizing system



Dec. 19, 1933. BARTHELEMY 1,940,161

SYNCHRONIZ ING SYSTEM Filed April 2l, 1931 3 Sheets-Sheet l 1933- R.BARTHELEMY V SYNCHHONIZING SYSTEM Filed April 21. 1931 a Sheets-Sheet 2IHI WU Q3 ip A 1616 Patented Dec. 19, 1933 PATENT OFFICE SYNCHRONIZINGSYSTEM Rene Barthelemy, Fontenay-aux-Roses, France, minor to CompagniePour La Fabrication Des Compteurs Et Materiel DUsines A Gas,

Montrouge, France, a. joint-stock company of France- Application April21, 1931, Serial No. 531,794, and in France May 21, 1930 11 Claims. (Cl.178-495) Several of applicant's previous patents disclose a remotelycontrolled synchronizing device to which is transmitted a current ofvery short duration termed top repeated at equal intervals of the orderof 1 of a second inthe case of telecinematography and which sets up anappropriate local oscillation.

The present invention has reference to a method and means enabling thelocal oscillation to be started solely through the agency of thesynchronizing top, to the exclusion of the other signals emitted by thesending apparatus and which are generally transmitted on the samecarrier wave as the synchronizing signal.

The principle oi the invention consists in produclng by means of thesynchronizing top a modulation of the carrier wave which corresponds toa variation 01! the virtual value of said wave of opposite sign to thatwhich would be produced by the television signals. To these twomodulations correspond two variations of opposite sign of the meancurrent detected in the receiver and with this difference of signs it iseasy to eliminate the effects of the television signals on thesynchronizing system. I

A simple means for enabling the two sorts of signals to bediiierentiated at the sending end consists in causing the top tomodulate by momentarily raising the plate voltage of the oscillatingvalve, whereas the modulated television signals are applied to the gridcircuit of said lamp through the medium of a suitable impedance betweenthe time intervals which separate two successive tops; this kind ofmodulation generally lowers the virtual current in the aerial.

A further object of the invention is to increase the security ofselection by mounting in the deteeter circuit a stopper" circuit tunedto the frequency of the synchronizing top and from the ends of saidcircuit is tapped the synchronizing voltage of suitable frequency, phaseand am.- plitude, which may then be applied, amplified or not, to themotor to be synchronized or any other equivalent system.

Several embodiments of the invention have been illustrated in theaccompanying drawings wherein:

Fig. 1 illustrates a transmitting device modulated according to theinvention.

Fig. 2 illustrates a suitable receiver for use with the transmittingdevice of Fig. 1.

Fig. 3 illustrates a modified circuit arrangement for the receivingdevice of Fig. 3.

Fig. 4 illustrates a further modification of the receiving device ofFig. 3.

Fig. 5 is a graph of the oscillations received by the device of Fig. 4.

Fig. 6 is a graph of the oscillations after selection effected by thedevice of Fig. 4.

Fig. 7 is a circuit arrangement of an automatic device for regulatingthe grid bias of the receiver of Fig. 4, and

Fig. 8 illustrates a modification of the device of Fig. 7, and Fig. 9 amodification of the device of Fig. 8.

In the device of Fig. 1, an oscillating valve 0 (which may be replacedby a bank of valves and may be followed by a high frequency amplifier ifhigh powers are to be obtained) produces the continuous wave of suitablefrequency by means of conventional reaction couplings, for example theelectromagnet coupling of an oscillating cir cult constituted by thecoil B and the condenser K with an inductance Ci mounted in the gridcircuit. Another suitable inductance A coupled to the coil B transmitsthe energy to the aerial, an earth having been featured at T. The modu--lation of the apparatus by the television oscillations is accomplishedby applying the modulating voltage coming in at M and N to theresistance R which may also be an inductance. A very small capacity Clets through the high frequency carrier current. Modulation is thuseffected by variation of the grid potential and it is observed that thevirtual current in the aerial decreases when the strength of said.modulation is increased.

Said modulation is discontinued at each complete scanning of the image.for a very short interval of time, during which time interval thesynchronizing top" is transmitted. To this end, a switch Z, rotatingsynchronously with the spindle of the scanning disc, breaks the currentfed by a direct current source E to the primary P of a transformer, atthe exact moment when the television modulation is interrupted. Theconnec tions being suitably established, an additional voltage, lastinga very short length of time, for example 1/10,000th of a second, isintroduced by the secondary S into the plate circuit of the oscillatingvalve and is added to the normal direct voltage. The virtual current inthe aerial is suddenly increased and such excess current easily attainsa value equal to the ordinary current. The current resumes its normalvalue when the energy stored up in the transformer is practicallydissipated by the valve. Then the grid modulation starts again arid thedirect current source E again feeds the primary P, the time forestablishing the Bill necessary current being calculated so as to be ofthe order of of a second.

The excess voltage may be introduced into the plate circuit in any othermanner without departing from the present invention. Thus, the drawbacksattendant on a switch breaking a certain current may be avoided bysubstituting therefor the filament-plate circuit of a three electrodevalve and by using the synchronous commutator to vary considerably thegrid bias without breaking the current.

At the receiving end, the signals will be selected by using the detectedcurrent, or a current proportional thereto, after amplification. Saidcurrent 2' generally flows through the plate of a valve and an anoderesistance or impedance p (Fig. 2). A fraction r of said resistance willbe used to start the local oscillation derived from the neon tube L, thecondenser Y, the resistance D and the source P, which device wasdisclosed in applicants U. S. application Serial No. 415,537 filedDecember 20th, 1929.

The potential difference used will he ran, it will dwindle to a verysmall value at the moment when the top" is received, it will be higherin the absence of any modulation and its mean value will increase againwhen the television modulation is applied. Thus if said voltage rimounted in series with the discharge tube be opposed to the voltagesupplied by the local source P, the latter may be adjusted so that thetube will light up each time ri decreases sufliciently, that is to sayat each top, while said tube remains unresponsive on the contrary to anyincrease of ri, that is to say to the television modulation.

Another object of the invention is to enable the two types of signals tobe selected with complete security. Its principle is based on thecombination of an impedance (in general a resistance) through whichfiows the said plate current, with an auxiliary electromotive force anda system having a more or less perfectly unilateral conductabilitysimilar to a detector.. It will be understood a priori that with theconnections suitably established and for a suitable value of theauxiliary electromotive force, the detector can choke all the televisionoscillations and only let through the synchronizing signal.

In the device illustrated in Fig. 3 for selecting the two types ofsignals mentioned above, the detector system is constituted by thefilamentgrid space of a triode S.

The plate current i of the detector valve D flows through the resistanceR and produces a difference of potential Ri which decreases by at leastone quarter of its valve upon receptionof a synchronizing top. The gridof the valve S is subjected to said potential difference Ri through themedium of a grid biassing battery E.

The voltage of said battery is such that a negative potentialis-impressed on the grid of the valve S (for the mean value of R2corresponding to the modulating television signals) which annuls theplate current of said valve S. Under these circumstances, said signalshave no effect on the transformer T. The incoming synchronizing signalcauses R2 to fall appreciably in value during the duration of saidsynchronizing signal, which moreover is very short, and the gridpotential of the valve S rises during this time to a higher valuethereby giving rise to an anode current which flows through the primaryof the transformer T. The making or breaking of this current generatesan electromotive force in the secondary which is utilized to light upthe pilot lamp disclosed in certain of my co-pending applications, andin particular in the aforementioned application Serial No. 415,537 filedDecember The condenser K shunted across the ends of the primary of thetransformer T constitutes with the self-inductance of said primary thestopper circuit referred to above and still further promotes selectionof the signals.

In this manner, by using a suitable bend of a characteristic curve of avalve and an auxiliary voltage, it is possible to select two types ofsignals modulating alternately and in different directions the samecarrier wave.

The television signals are transmitted to the succeeding amplifyingvalves such as BF by means of any suitable coupling, as for example acondenser C.

The invention is likewise concerned with a modified circuit arrangementof the detector-selector at the receiving end.

The current variations detected by television are transmitted andamplified by an amplifier which must be designed to faithfully reproducea large range of frequencies; in Fig. 4 the current oscillationsdetected-are applied through the medium of a condenser C and aresistance R on the controlling grid g of an amplifying valve. In Fig. 5have been illustrated the voltage oscillations which take place in theresistance R. During the whole time of transmission of the televisionsignals, the grid voltage drops by an amount of mean value a. Theoscillations of maximum amplitude are for example (ua+u:), then uponpassage of the synchronizing signal, the grid voltage increases by uswhich is substantially higher than the value m.

If, in conformance with the invention, the valve is used as a detector,the television signals will be eliminated and, the grid being suitablybiassed, only the oscillations of the anode current i in the transformerT due to the synchronizing signals will be observed (Fig. 6). Withsufilcient negative grid bias, the plate current will be annulled evenin the case of the strong- Obviously the valve might include otherelectrodes and the grid be charged through the medium of anothercoupling without departing from the spirit of the invention.

The current pulsations obtained may then be readily used forsynchronizing with extreme accuracy the rotation of the televisionscanning disc, by using the devices disclosed in others of my patents.

The above described method of separating synchronizing from televisionsignals by using the bend of the characteristic curve of a receivingvalve and negatively biassing its grid, requires that the bias shall besufficient to prevent television signals from producing oscillations inthe plate circuit of the valve, but it must not be so great that thesynchronizing signal is also choked. The mean value of the biassingvoltage must therefore be determined as a function of the current at thereceiving end. Such adjustment is readily accomplished but if thecurrent at the receiving end is variable, as is frequently the case, inwireless transmission, this operation becomes diflicult.

The invention is likewise concerned with an automatic adjustment for thebiassing voltage obtained by producing said voltage by the receivedcurrent itself, of course after suitable transformation.

This is achieved by producing in the amplifier of the receiver,generally in the low frequency stage, a voltage proportional to the meanamplitude of the detected oscillations, in converting said alternatingvoltage into a substantially direct voltage by means of a valve andfilter, (which may be only a simple condenser) and in applying saidvoltage in a suitable direction to the grid circuit of the signalselecting valve.

In Fig. 7 a television receiver having for example 3 stages ofamplification includes a detector valve 1 and two amplifying valves 2and 3, the latter acting on the luminescent tube N. Another valve 4having suitable grid bias is provided for selecting the synchronizingsignal, the amplitude of which is considerably greater than that of thetelevision signals, and the brief pulsations of the synchronizing "topare converted in the anode circuit of said valve into oscillations oflonger duration, by means of the condenser K and the transformer T inthe manner indicated above; these long oscillations can then be utilizedin the synchronizing device.

Automatic biassing of the grid of said valve 4, proportional to thecurrent received, is secured according to the invention by applying avoltage u derived from the resistance R. There flows through saidresistance a direct current caused by the oscillations which have beenimpressed on the valve N and which have been applied, through the mediumof the transformer T, to a valve V which may be of any type of currentrectifier. A condenser C of large capacity enables a practically directvoltage to be obtained which follows only the slow fluctuations atreception and which,

contains no high frequency terms produced by the modulation. The bias uis therefore proportional to the mean current received taken over a verylong time interval.

Another arrangement based on the same principle, consists in using therectifying properties of the triode 4 itself to obtain a valve effectand in using the voltage taken from the filament plate circuit in asuitable filter, the whole or part of the purified voltage derivedtherefrom being used to bias the grid in the manner desired.

Fig. 8 shows the detail of this device, which in addition to theadvantage of simplicity only uses the energy proportional to thesynchronizing signal, to the exclusion of the television signals, andfeeds to the synchronizing circuit power which within wide limits isindependent of the power received. This quality is of great value forthe stability of the images in television.

The television amplifier receiver supplies at S a composite voltage onecomponent of which is the television and synchronizing signalsalternately, the amplitude of the latter being considerably greater thanthat of the television signals. This voltage is applied to theresistance 9 connecting the grid to the usual common point. An auxiliarybiassing battery P which is not involtage R2, decreases.

dispensable, is so designed that in the absence of the signals, theanode current i supplied by the source U is practically nil. Under theeffect of the incoming signals, the current 1 assumes a mean value whichis not nil and the flow of said current in the resistance R produces avoltage drop which biases the grid negatively with respect to thecathode.

As said current i is formed by successive pulsations, if a condenser Kof sufilcient capacity be mounted at the ends of the resistance R, thereis created a biassing voltage proportional to the mean value i reckonedover a fairly long interval of time.

The value of R is so chosen moreover that the bias obtained shall besufficient so that television signals proper shall take no part inproducing the anode current and that only' the synchronizing signals ofsuificient amplitude shall produce the anode current and, consequently,automatically maintain the biassing voltage. Under these conditions,only the pulsations due to synchronization are transmitted to the motorM or to an additional amplifier through the medium of the transformer Tcombined with the condenser C. It is thus seen that the influence of thetelevision modulation is completely eliminated.

Moreover the intensity of the synchronizing oscillations transmitted tothe motor M is substantially constant, which is explained by the factthat if the incoming signals increase in strength, for example, thebiassing voltage increases and, simultaneously, the real anode voltage,which is equal to the voltage U minus the These two efiects arecumulative, if the valve characteristics be considered, and limit theincrease of power in the anode circuit which would be introduced by theincrease in the strength of the signals and which would exist were theplate and grid potentials constant.

The circuit may be modified in several ways without departing from thescope of the invention. Thus instead of the simple resistance-capacityfilter disclosed, a filter having several cells with a large timeconstant (not shown) may be usei in Fig. 8 has been disclosed anindependent filament heating battery A but instead of said independentheating source the device of Fig. 9 may be used in which the cathode Cof the valve 4 is indirectly heated by a filament F connected to thesupply mains G. The advantage of this modification is that the potentialof the cathode C can be adjusted at will.

I claim:

1. In a device for transmitting synchronizing signals using a carrierwave which is likewise modulated by a difierent type of signals such astelevision signals, the combination of an oscilla ticn generating triodehaving an input and an output circuit, means for impressing the carrierwave frequency on the input circuit of said valve, means for impressingtelevision signals on the input circuit of said valve to modulate saidcarrier wave, and periodically operative means for impressing thesynchronizing signals on the output circuit of said valve, thetransmission of the television signals being discontinued during thetransmission of the synchronizing signals.

2. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals, such as television signals, the combination of an oscillationgenerating valve, means for impressing the carrier wave frequency on thegrid circuit of said valve, means for impressing said television signalson the grid circuit of said valve, periodically operative means forimpressing the synchronizing signals on the plate circuit of said valve,the transmission of the television signals being discontinued during thetransmission of the synchronizing signals, receiving apparatus includinga triode and means for impressing said modulated signals on the inputside thereof, and means associated with said triode for deriving fromthe output side thereof diiferent potentials corresponding to thetelevision signal and synchronizing signal modulations respectively.

3. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals such as television signals, the combination of an oscillationgenerating triode, means for impressing the carrier wave frequency andmodulating television signals on the input circuit of said triode,periodically operative means for impressing the modulating synchronizingsignals on the output side of said triode, the transmission of saidtelevision signals being discontinued during the transmission of saidsynchronizing signals, a receiving triode on the input side, of whichsaid modulated carrier wave is impressed, and an impedance mounted inthe plate circuit of said receiving triode and across which a potentialmay be derived which is greater in the case of television signalmodulations than in the case of synchronizing signal modulations.

4. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals such as television signals, the combination of means fortransmitting a carrier wave, means, alternating in operation, forproducing modulations of said carrier wave by television signals andsynchronizing signals respectively, said two kinds of modulations beingof opposite signs with respect to the virtual value of said carrierwave, a receiving rectifying triode on the input side of which saidmodulated carrier waves are impressed, an impedance mounted in the platecircuit of said rectifying triode, and across which a higher potentialis created on reception of said television signal modulations than onreception of said synchronizing signal modulations, an additionaltriode, a biassing battery mounted in the grid circuit of saidadditional triode and adapted in conjunction with said impedance to biassaid grid negatively, said biassing battery being adapted when assistedby the potential across said impedance due to reception of saidtelevision modulations to bias the grid of said rectiher so stronglythat substantially no current flows in the plate circuit of saidrectifier whereas current flows therethrough when the potential acrosssaid impedance drops upon reception of the synchronizing modulations.

5. A device according to claim 4, in combination with a stopper circuitmounted in the plate circuit of said rectifier and tuned to thesynchronizing signal frequency.

6. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals such as television signals, the combination of means fortransmitting a carrier wave, means, alternating in operation, forproducing modulations of said carrier wave by television signals andsynchronizing signals respectively, said two kinds of modulations beingof opposite signs with respect to the virtual value of said carrierwave, a receiving triode including a grid circuit on which saidmodulated carrier waves are impressed, an impedance, and a biasingbattery mounted in series with said impedance in said grid circuit, saidbattery being adapted to bias said grid negatively to such an extentthat only the synchronizing signal modulations, but not the televisionsignal modulations, are of sufficient amplitude to permit a platecurrent to flow.

7. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals such as television signals, the combination of means fortransmitting a carrier wave, means, alternating in operation, forproducing modulations of said carrier wave by television signals andsynchronizing signals respectively, said two kinds of modulations beingof opposite signs with respect to the virtual value of said carrierwave, receiving apparatus including a triode, an impedance mounted inthegrid circuit of said triode, means for impressing the television andsynchronizing modulations on the grid circuit of said triode, means forconverting incoming television and synchronizing modulations into directvoltage, and means for applying said direct voltage across saidimpedance to bias said grid whereby only the synchronizing signalmodulations are of suflicient amplitude to produce a current on theplate circuit of said triode.

8. In a device for transmitting and receiving synchronizing signalsusing a carrier wave which is likewise modulated by a different type ofsignals such as television signals, the combination of means fortransmitting a carrier Wave, means alternating in operation, forproducing modulations of said carrier wave by television signals andsynchronizing signals respectively, said two kinds of modulations beingof opposite signs with respect to the virtual value of said carrierwave, receiving apparatus including a rectifying triode, a plurality ofamplifying triodes and a synchronizing signal selecting triode on thegrid circuit of which the television and synchronizing signalmodulations are impressed after rectification and amplification, animpedance mounted in the grid circuit of said synchronizing signalselecting triode, means for converting the rectified and amplifiedsignal modulations into direct voltage, and means for applying saiddirect voltage across said impedance to bias the associated grid wherebyonly the synchronizing signal modulations are of sufficient amplitude toproduce a current in the pate circuit of said synchronizing signalselecting triode.

9. A device according to claim 8, in which said means for converting therectified and amplified modulations into a direct voltage comprise arectifying tube and a filter circuit in circuit therewith.

10. In combination with a device according to claim 4, a filter circuitmounted in the plate cir cuit of said additional triode and adapted tochoke any television modulations that may get through to the platecircuit of said additional triode.

11. In combination with a device according to claim '7, independentheating means for the-cathode of said triode.

RENE BARTHELEMY.

